chapter eight Investigating indoor environment problems As indicated in previous chapters, built environments are subject to a num- ber of potentially significant indoor air quality/indoor environment (IAQ/IE) problems that may cause acute symptoms, long-term health risks, discomfort, or odor. With the exception of severe cases of acute illness or unpleasant odors, most problems (or potential problems such as radon) go unrecognized. In the case of residential and nonresidential buildings, a need to conduct an IAQ/IE investigation develops only after occupants become aware that health and other problems may be associated with home or work environments. Awareness development is rapid when an odor problem or some type of physical discomfort occurs. In most cases, building occupants do not suspect a causal relationship between acute and chronic illness symp- toms (which characterize classical air quality-related symptoms) and their building environment. High prevalence rates of sick building syndrome (SBS)-type symptoms in noncomplaint buildings suggest that most individ- uals so-affected do not realize that their building/work environment is in any way responsible. I. Awareness and responsibility A. Residential buildings Illness symptoms associated with exposure to formaldehyde (HCHO), com- bustion by-products such as carbon monoxide (CO), inhalant allergens, and long-term health risks associated with elevated radon levels are major IAQ/IE problems in residential environments. When such problems occur, it is the individual homeowner’s/lessee’s responsibility to recognize that a problem exists and seek professional assistance to identify and resolve it. © 2001 by CRC Press LLC In our society an individual experiencing the relatively minor symptoms of headache, fatigue, and mucous membrane irritation seeks to achieve relief by using over-the-counter or prescription medication. The emphasis is on symptom relief rather than identifying and mitigating causal factors. Such a symptom amelioration approach assures the problem will persist. How may homeowners/lessees develop an awareness that health prob- lems may be due to contaminant exposures in their home environments? Awareness, in most cases, comes as a matter of chance — in the form of national or local news reports, internet sites, conversations with acquaintan- ces, or physician suggestions. Awareness requires some degree of education on the part of homeown- ers/lessees, and physicians (if medical assistance is sought). Factors that suggest illness symptoms may be associated with one’s home environment are summarized in Table 8.1. Listed factors represent common sense epide- miological observations. They reflect exposure/response relationships that are either simply helpful or essential in determining a causal relationship between building environments and persistent health problems. An individual must be exposed to concentrations sufficient in magnitude to experience symptoms caused by gas/particulate-phase contaminants of either a chemical or biological origin. Exposure is related both to the con- centration of causal substances and to duration. As a consequence, exposures and illness symptoms can be expected to diminish when a building is ven- tilated, and when individuals are away from home for a period of time. On the other hand, individuals who spend the most time at home commonly experience more severe symptoms. As indicated in Table 8.1, other factors also suggest a potential causal relationship with one’s home environment. Multiple individuals experienc- ing similar symptoms indicate common exposures, as do visitors reporting similar symptoms. Houses that experience high moisture levels are known to be at special risk for mold infestation and high dust mite populations. Significant HCHO exposures have occurred, and in some cases continue to occur, in mobile homes. Table 8.1 Factors Indicating Health Problems May Be Associated with Exposures to Contaminants in Residential Environments Symptoms diminish in severity when building is ventilated by opening windows. Symptoms diminish in severity or resolve completely when occupants are away from home for several days, and recur upon returning. Symptoms show a seasonal pattern, that is, associated with the heating/cooling season, building closure conditions, or operation of heating/cooling appliances. Similar symptoms occur in several or more building occupants. Symptoms are more severe in individuals who spend the most time at home. Symptoms develop after moving into a new home (not necessarily a new house). Residential environment subject to severe moisture and/or mold infestation problems. Symptoms experienced by visitors. © 2001 by CRC Press LLC For individuals experiencing IAQ/IE-related illness problems in their homes, it is, in most cases, very difficult to make the associations that seem so logical in Table 8.1. Nevertheless, some association must be made before the problem can be professionally investigated and mitigation efforts recommended. Longer-term health risks like those associated with radon and environ- mental tobacco smoke (ETS) require an educated public that recognizes the need for conducting radon testing in their homes, implementing mitigation measures when elevated radon levels occur, and minimizing exposure to tobacco smoke. B. Nonresidential buildings Occupants of nonresidential office, commercial, and institutional buildings must also develop an awareness that illness symptoms may be associated with their building environment. Awareness of potential IAQ/IE problems in such buildings is more likely to occur because: (1) of the larger population base and potential for interaction among occupants, (2) these buildings are prone to a larger variety of problems than residential buildings, (3) building thermal and ventilation conditions are less under the control of occupants, (4) many buildings are poorly ventilated or have poor thermal control, which may contribute to vocal occupant dissatisfaction, and (5) of “odor” problems. Odor complaints often trigger investigations of unrelated illness symptoms. Investigations of IAQ/IE concerns are commonly conducted in non- residential buildings because the factors described above increase the prob- ability that IAQ and other environmental complaints will be reported to building management. The relationship between health symptoms and one’s building/work environment is more clear cut than is the case for residential environments. In most instances, symptoms resolve within a few hours after leaving the building/work environment and begin anew within an hour or two after beginning work the next day. Symptoms typically do not occur over week- ends and during vacations. Symptom prevalence is often high as well, with 15+% of building occupants reporting symptoms in building investigations and questionnaire studies. II. Conducting indoor environment investigations The task of investigating building-related health, comfort, and sometimes odor complaints falls to a variety of local, state, and federal public or occu- pational health agencies, and increasingly, private consultants. Typically, residential complaints are investigated by local and state public health agen- cies. Nonresidential complaints are more commonly investigated by staff of private consulting firms. Health hazard evaluation teams from the National Institute of Occupational Safety and Health (NIOSH) conduct investigations © 2001 by CRC Press LLC of building environments on request when workers in schools, office build- ings, etc., are involved. The primary goal of conducting building investigations is to identify and mitigate IAQ/IE problems and prevent their recurrence. Successful con- duct of building investigations requires that investigators have (1) extensive knowledge of buildings and building systems, (2) a broad understanding of the nature of IAQ/IE problems and factors that contribute to them, (3) an understanding that IAQ/IE investigations have both political and technical dimensions, (4) knowledge of environmental testing procedures and their limitations, and (5) knowledge of investigative protocols and their applica- tion to conducting successful IAQ/IE investigations. A. Residential investigations Residential IAQ/IE problems are, in theory, easier to diagnose than those that occur in nonresidential buildings. In many, but not all, cases they are more easily resolved. Residential structures are smaller and more simply designed, and activities that occur within them, and equipment and materials used, are fewer and less diverse. The design and operation of mechanical heating/cool- ing systems are also less complex than in nonresidential buildings. To successfully conduct an investigation of residential IAQ/IE com- plaints, an investigator must know what the most common problems are, various aspects of housing construction, the location and operation of heat- ing and cooling systems, aspects of human behavior, and what can go wrong in heating/cooling system operation and building maintenance. Unfortu- nately, many of the tools required to conduct a successful residential IAQ/IE investigation are only acquired by an investigator after many years of con- ducting investigations. Though dwellings are simple structures, each has its own unique construction and renovation history as well as history of occu- pancy. With the possible exception of many manufactured houses, IAQ/IE investigations will rarely be the same for any two houses. 1. Investigative practices There are three basic approaches to conducting residential IAQ/IE investi- gations. These can be described as (1) an ad hoc or “seat of the pants” approach, (2) conducting air testing only, and (3) a systematic approach that is designed to identify and resolve problems. a. Ad hoc approach. The ad hoc approach is used by investigators who have had little or no experience in responding to homeowner complaints. Such investigations are conducted by personnel in small public health depart- ments where few resources are available and where housing investigations are often of the “nuisance” type. They are also conducted on occasion by private consulting personnel who have little experience. Such investigations have a limited probability of identifying and mitigating IAQ/IE problems. © 2001 by CRC Press LLC b. Air testing. At a somewhat higher plane are investigations con- ducted by local and state public health departments in which the primary focus is air testing. Such investigations are done in response to a home- owner/lessee request to determine by air testing what might be wrong with their home. Air testing is usually limited to a few well-defined contaminants for which methodologies and equipment are readily available, e.g., CO, HCHO, and mold, and which have a history of being a potential cause of contamination and health problems in dwellings. Generic air testing, as an investigative protocol, has significant limita- tions. Low contaminant levels based on one-time sampling are often inter- preted as indicating that a problem does not exist. Such interpretations ignore the often episodic nature of contaminant emissions and concentrations as well as seasonal variations that occur with CO, HCHO, and mold. Air testing results are often compared to guideline values that may not be sufficiently health-based or protective of sensitive populations. Air testing tends to be hampered by the “magic number” syndrome: levels above guideline values are unsafe; levels below them are safe. Unfortunately, safe or acceptable levels of exposure that protect the most sensitive or vulnerable populations are less clear cut than guideline values, which are often based on what can be reasonably achieved. c. Systematic approaches. To successfully conduct an IAQ/IE investi- gation in a residential environment, it is essential that the investigator approach the problem in a systematic manner. This includes pre-site-visit information gathering, an on-site investigation and occupant interview(s), conducting air/surface dust testing when appropriate, and evaluating poten- tial causal factors and mitigation requirements when the on-site investigation has been completed. Pre-site-visit information gathering is typically conducted in a phone interview with an adult building occupant (preferably the female head of house). This limited interview should be designed to elicit information on the perceived nature and history of the problem; symptom types and pat- terns; house type, construction, age, and recent changes and renovations; previous investigations and results; and any mitigation efforts. Information gathered in the phone interview may be used in initial hypothesis formation and in suggesting air testing and environmental sampling needs. The on-site investigation typically provides information essential to suc- cessfully diagnosing an IAQ/IE problem. The on-site investigation should include a careful inspection of both the interior and exterior of the building. This includes basement and crawlspace (and, in some cases, attic as well). The investigator should be cognizant of any distinctive or unusual odors that may indicate the nature of the problem or factors contributing to it. These include chemical odors, pesticides, new carpeting and other new materials, mold odor, etc. The investigator should be able to recognize mate- rials, equipment, etc., that may be a source of health-affecting contaminants. © 2001 by CRC Press LLC These would include large volumes of pressed wood products bonded with urea–formaldehyde resins (e.g., particle board, hardwood paneling, medium-density fiber board [MDF]); malfunctioning space and/or water heaters; mold-infested materials; hobbies/crafts (e.g., silk screening, stained glass, etc.); pets; insect infestations; recent pesticide applications; lead-based paint; etc. The inspection should include an evaluation of any structural problems such as water-damaged interior/exterior materials, rotting timbers, damaged gutters, cracks/holes in brick veneer, and wet basements/crawlspaces. It should include a site evaluation as well. Site conditions of note include mod- erate to heavy shade, poor site drainage as evidenced by ponding after rains, moss growth, frost heaving, capillary wicking on substructure walls, etc. Heating/cooling system appliances, including hot water heaters, should be inspected, as well as associated flue systems and supply and cold air duct systems. Evidence of flue gas spillage (in the absence of CO measurements) can be determined from condensation stains and corrosion on draft hoods and flue pipes as well as the design and assembly of flue pipes. The location of furnace/air conditioner/blower fans and return air ducts is important in conducting a building investigation. The presence of such systems in musty basements or wet crawlspaces provides a pathway for the transport of mold spores from an infested source to spaces throughout the home. Ductwork in slab-on-grade houses should be inspected (by opening supply air registers) to determine whether water entry occurs, if insect/dust contamination is present, and what materials ducts are made of. During the on-site investigation, an intensive interview should be con- ducted with an adult occupant to better define the nature of health problems experienced as well as to gain additional information on various factors observed during the inspection of the interior and exterior of the home. This interview may provide information on aspects of the inspection that might require more detailed evaluation. Air/environmental testing may be conducted to confirm and elucidate the nature of the problem. Air testing for HCHO is desirable if evidence indicates that occupants have been experiencing symptoms consistent with the presence of significant HCHO sources. Carbon monoxide testing is appropriate if symptoms are characteristic of CO exposures or there is visible evidence of flue gas spillage. Air testing for mold using both culturable/via- ble and total mold spore sampling is desirable if the building environment has been subject to moisture problems with or without evident mold infes- tation. The use of a portable flame ionization detector (FID) to determine sources of methane would be appropriate if a sewer gas problem appears to exist without an evident source. Surface dust sampling and monoclonal antibody testing for dust mite, pet, and cockroach allergens may be appro- priate in cases where health histories are suggestive of inhalant allergens. A role exists for air testing and environmental sampling in conducting resi- dential building investigations. That role is to confirm a hypothesis or to more fully evaluate the nature of a problem. © 2001 by CRC Press LLC After the on-site inspection, occupant interview, and air testing/envi- ronmental sampling, the investigator should evaluate all information obtained during the investigation. During this evaluation process, he/she should determine whether symptoms/health problems/complaints are con- sistent with observations made during the inspection, as well as with results of air/environmental sampling. 2. Diagnosing specific residential indoor environment problems Though the nature of residential IAQ/IE complaints varies, only a relatively few contaminants are responsible. These include biological contaminants such as mold and allergens produced by dust mites, pets, and insects; HCHO; CO; pesticides; lead dusts; sewer gases; and, increasingly, soot pro- duced by candle burning. Complaints may include significant health effects or be of a nuisance nature. Diagnostic criteria used to evaluate residential indoor environment problems are summarized below. a. Biological contaminants. Biological contaminants, as indicated in Chapters 5 and 6, are the major cause of allergy, asthma, and recurring sinusitis in tens of millions of North Americans annually. These ailments have characteristic symptoms and clinical findings that can be used to identify potential causal agents. Individuals affected often have a family history of allergy or asthma and test positive to specific allergens in standard allergy testing. Building diagnoses associated with allergens is best conducted in con- sultation with a physician trained in allergy or immunology. When such consultation is impractical, the investigator should use professional judg- ment in evaluating the potential cause of allergy/asthma/sinusitis among occupants of a residence. Risk factors that can be used to evaluate biological contaminants as potential causes of allergy/asthma/sinusitis associated with residential environments are summarized in Table 8.2. b. Formaldehyde. Fortunately, HCHO is less likely to cause IAQ- related health complaints today than at any time in the past three decades. Because of changes in the use of construction materials and improvements in products bonded with urea–formaldehyde resins, indoor HCHO concen- trations (even in many new dwellings) are relatively low and are unlikely to cause health problems. Despite this, HCHO may cause symptoms in sensitive individuals in environments such as new mobile homes constructed with urea–formaldehyde-bonded wood products and homes with new wood cabinetry or furniture. Factors that suggest HCHO exposures may be respon- sible for reported health complaints include: (1) symptoms characterized by eye and upper respiratory system irritation, headache, and fatigue; (2) symp- toms more severe on warm, humid days; (3) potent HCHO-emitting sources present; and (4) HCHO levels determined under near-optimum testing con- ditions (closure, humidity >50%, temperature 22 to 25°C, moderate outdoor conditions) ≥ 0.05 ppmv. © 2001 by CRC Press LLC c. Carbon monoxide. Flue gas spillage and associated exposures to CO and other combustion by-products commonly occur in residences. Such problems have been reported in residences of all ages; they are, however, more likely in older buildings. Carbon monoxide exposures are characterized by symptoms of headache, extreme fatigue, sleepiness/sluggishness, and even nausea. Risk factors include the presence of combustion appliances that show some evidence of malfunction (loose flue pipes, flue pipe condensation staining and/or corrosion); symptoms associated with the heating season; measured CO levels >20 ppmv; carboxyhemoglobin (COHb) levels >2% in nonsmokers not exposed in the workplace; and high CO levels emanating from supply registers (indicating cracked heat exchangers). Extreme care must be taken in diagnosing a CO problem. Flue gas spillage is, by its very nature, episodic. As such it is not uncommon to measure very low CO levels in a residence even though a CO exposure problem exists. Blood tests for COHb may be desirable when a building occupant reports symptoms. As CO exposures are common in small indus- Table 8.2 Risk Factors for Biological Contaminant-Associated IAQ/IE-Related Health Problems Contaminant Risk factor Mold Obvious active/past mold infestation on building materials Building history of water damage Wet building site Musty odors Culturable/viable airborne mold test results (uninfluenced by outdoor mold sources) >1000 CFU/m 3 Sample results dominated by one or several mold genera Total mold spore counts >10,000 S/m 3 Positive allergy tests Dust mites Damp/moist interior building conditions High (>2 µ g/g) mite allergen levels in floor dust samples Positive allergy tests Pet danders Presence of pets in or near home House history of pets (without pets necessarily being present) Positive allergy tests High allergen levels in floor dust samples (cat ≥ 1 µ g/g) Other allergens Evidence of organisms present Cockroach, birds, rodents, crickets, spiders Positive allergy tests High allergen levels in floor dust samples (cockroach ≥ 2 U/g) © 2001 by CRC Press LLC trial environments, workplace exposures should also be evaluated in the context of COHb test results. d. Pesticides. As indicated in Chapter 4, a variety of pesticide expo- sure problems occur in residences. These may be due to indoor application of pesticide products or passive transport of pesticides from the outdoors. Acute pesticide-caused symptoms are typically associated with applications within the home. Diagnosis of an exposure problem requires a knowledge of recent pesticide usage and the type used. Symptoms may be due to active compounds, inert ingredients, or both. Because of low vapor pressures of pesticidal compounds, air testing will generally not show significantly ele- vated concentrations. Nevertheless, it may be desirable to conduct air testing in response to a homeowner’s request or to confirm that air levels are not excessive. The level of indoor contamination and potential for future expo- sure may be determined from floor dust or surface wipe samples. High pesticide residue concentrations in such samples may indicate the need for significant remediation measures. e. Lead. Exposure to lead-contaminated dust and soils is the major cause of pediatric lead exposure and poisoning. Building investigations asso- ciated with elevated blood lead levels and frank symptoms of lead poisoning are commonly conducted by public health personnel and, in some cases, private consultants. It is desirable for investigators to have obtained records and reports of blood lead tests and physician diagnoses and recommenda- tions. The investigator should conduct a complete residential risk assessment for potential lead exposure using the protocol described for investigation of elevated blood lead levels in the 1995 HUD (Department of Housing and Urban Development) guidelines for lead in housing. In conducting such investigations, all potential sources of lead are taken into consideration. These include lead-based paint, lead-contaminated dusts and soil, water, lead associated with hobbies and crafts, lead brought home from work environments, lead-containing ceramics or glassware, home remedies, can- dles with lead-containing wicks, etc. f. Miscellaneous nuisance problems. Sewer gas odors are the most common IAQ/IE nuisance problems experienced in residences. Sewer odors are usually associated with dry sink/drain traps or the absence of drain traps in air-conditioning condensate drain lines connected to sewer lines. Sewer gas problems are easily resolved by locating all sink/drain traps that lead to sewer lines and filling them with water. Air testing with a portable flame ionization detector (FID) is desirable when dry traps cannot be located easily. An increasingly important nuisance problem in North American homes is soot deposition on wall and ceiling surfaces associated with the frequent burning of candles and incense. Soot deposition occurs on surfaces with differential temperature conditions (e.g., around wall heating units, on wall © 2001 by CRC Press LLC surfaces with thermal bridges [see Chapter 6]). Soot and wick fragments can be identified microscopically. B. Nonresidential investigations The investigation of IAQ/IE complaints in nonresidential office, commercial, and institutional buildings is a much more difficult task than investigating residential problems. Nonresidential buildings represent much more com- plex environments in terms of the larger populations of individuals involved; a greater diversity of contaminants and potential exposure sources; mechan- ical systems that provide heating, cooling, ventilation, and sometimes steam humidification; lack of individual control over thermal and ventilation com- fort; interpersonal dynamics between occupants and building management; and the often-multifactorial nature of health complaints in such buildings. However, principles employed in conducting residential and nonresidential investigations are, for the most part, similar. Investigative techniques and protocols used in problem building inves- tigations reflect the knowledge and experience of individuals conducting them. They also reflect the availability of resources of government agencies and private consultants that provide such services, as well as the resources of those requesting services on a fee basis. Early problem building investigations were conducted on an ad hoc basis. They were usually limited to brief discussions with building management, a building walk-through, and a few simple screening air tests. Increasingly, building investigations conducted by state government agencies and con- sulting companies that specialize in conducting IAQ/IE investigations have become more systematic. The purpose of an IAQ/IE investigation is, in theory, to identify and resolve complaints in a way that prevents them from recurring. However, building managers/owners may see the problem in different terms. They may view it in the context of occupant complaints only; i.e., the focus of their concern may be to mollify those who complain rather than identify and resolve the actual cause or causes. Consequently, they may request that a government agency or private consulting company conduct air testing to demonstrate to occupants their “good faith” in responding to occupant con- cerns. Such investigations are usually limited to providing screening mea- surements. Since contaminant levels in screening measurements are rarely above guideline values (with the exception of CO 2 ), air testing alone is often unsuccessful in identifying and resolving building-related problems. It is not uncommon for building managers to conclude from such testing that an IAQ/IE problem does not exist. The type of services that a building man- ager/owner requests is discretionary, whether it makes technical sense or not. 1. Investigative protocols for problem buildings A number of systematic protocols have been developed for conducting prob- lem building investigations in the U.S., Canada, and northern Europe. In the © 2001 by CRC Press LLC [...]... IAQ/IE-related complaints It includes multiple stages of investigation: pre-site-visit information gathering, on-site inspection of the building environment, assessment of occupant symptoms and complaints, assessment of HVAC system operation and maintenance, assessment of potential contaminant sources, and environmental measurements a Pre-site-visit information gathering Before beginning an on-site... determined from Figure 8. 2 A peak CO2 level of 80 0 ppmv would be equal to a ventilation rate of 20 CFM/person or approximately 10 L/s/person Figure 8. 2 Outdoor air ventilation requirements as a function of peak indoor CO2 concentrations (From Salisbury, S.A., in Weekes, D.M and Gammage, R.B., Eds., Proceedings Indoor Air Quality International Symposium: The Practitioner’s Approach to Indoor Air Quality Investigations,... Refrigerating and Air-Conditioning Engineers (ASHRAE) (Table 8. 6) and for indoor contaminants by the World Health Organization (WHO) and other bodies Guideline values for HCHO are summarized in Table 8. 7 Note the considerable range of acceptable levels of HCHO in indoor air It is notable that concentrations of 0. 08 to 0.12 ppmv Table 8. 7 Guidelines for Acceptable Formaldehyde Levels in Indoor Air Agency/government... _ Source: From Indoor Climate and Air Quality Problems, SBI Report 212, Danish Building Research Institute, Aarhus, 1996 With permission © 2001 by CRC Press LLC Chapter eight: Danish Building Research Institute Indoor Climate Survey 261 Readings ANSI/ASHRAE Standard 5 5-1 981 , Thermal Environmental Conditions for Human Occupancy, American Society for Heating, Refrigerating and Air-Conditioning Engineers,... 1 981 ASHRAE Standard 6 2-1 981 R, Ventilation for Acceptable Indoor Air Quality, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Atlanta, 1 989 ASTM, Guide for Inspecting Water Systems for Legionella and Investigating Outbreaks of Legionellosis (Legionnaires’ Disease and Pontiac Fever), American Society for Testing Materials, West Conshohocken, PA, 1996 Davidge, R et al., Indoor. .. Hygienist’s Guide to Indoor Air Quality Investigations, American Industrial Hygiene Association, Fairfax, VA, 1993 Spengler, J.D., Samet, J.M, and McCarthy, J.F., Eds., Indoor Air Quality Handbook, McGraw-Hill Publishers, New York, 2000, chaps 49, 52, 53 USEPA/NIOSH, Building Air Quality: A Guide for Building Owners and Facility Managers, EPA/400/ 1-9 1/003, DDHS (NIOSH) Publication No 9 1-1 14, Washington,... et al., Indoor Air Quality Assessment Strategy, Building Performance Division, Public Works Canada, Ottawa, 1 989 Kukkonen, E et al., Indoor Climate Problems — Investigation and Remediation Measures, Nordtest Report NT Technical Report 204, Helsinki, 1993 Light, E and Sundell, J., General Principles for the Investigation of Complaints, TFII-19 98, International Society of Indoor Air Quality & Climate,... recommended by the American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE), most ( 80 %) building occupants will be satisfied with building air quality © 2001 by CRC Press LLC Figure 8. 1 USEPA/NIOSH model investigative protocol for in-house personnel (From USEPA/NIOSH, EPA/400/ 1-9 1/003, DHHS Publication No 9 1-1 141, 1991.) The Building Diagnostics approach places primary emphasis... for Schools, USEPA, Washington, D.C., 1996 Woods, J.E et al., Indoor air quality diagnostics: qualitative and quantitative procedures to improve environmental conditions, in Design and Protocol for Monitoring Indoor Air Quality, ASTM STP 1002, Nagda, N.L and Harper, J.P., Eds., American Society for Testing and Materials, Philadelphia, 1 989 , 80 Questions 1 How can you know whether illness symptoms experienced... and 170.1 cm (67 in.) levels 10°C (< 18 F) in horizontal direction; 5°C ( . chapter eight Investigating indoor environment problems As indicated in previous chapters, built environments are subject to a num- ber of potentially significant indoor air quality /indoor. and envi- ronmental measurements. a. Pre-site-visit information gathering. Before beginning an on-site inspection, it is important to obtain information that will facilitate its con- duct the investigation and determine environmental sampling needs. Pre-site-visit information gathering may be used to provide building managers with problem-solving recommendations on a self-help basis (as is done